Method of making flexible tubing



Nov. 8, 1938. H. w. WEBB 2,135,651

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Patented Nov. 8, 1938 UNITED STATES METHOD OF MAKING FLEXIBLE TUBING Hartwell w. Webb, Flint, Mich, asaignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Application September 11, 1936, Serial No. 100,296

shape. It has been found that where a flexible tubing is made with the small triangular member spirally wound between the convolutions of the relatively broad member the tubing will have a tendency to "crack or "break" when given too small a bending radius. This cracking or breaking is objectionable in that the tube could not be easily restored to its original shape. In investigating the cause of this cracking or breaking it was found that if the relatively narrow triangular element of the casing was made with dished arcuate sides and the shape of the sides of the are made to conform with the rounded shape of the relatively broad member, a better casing could be made by bending or flattening the edge of the triangular member where it contacts with the broader element of the casing. This flattening or bending is caused by the rolls in. winding the wire to circular form when the casing is made. The triangular member before it is formed into the casing has its outer side curved or inwardly dished, but in the finished form of the cable the outer face is substantially flat or straight for the reason that the edges of the element (adjacent the broad element of the tubing) have been curled down or bent toward the casing. This curling down or bending of the arcuate edge gives a closer contact between the adjacent elements of the casing and also prevents the cracking or breaking of the cable when given a relatively short radius of curvature.

0n the drawing Figure 1 is a view of the wire the pairs of forming rolls.

Figure 2 is an enlarged sectional detailed view through the completed casing.

Figure 3 shows in section the finished wire rolled into triangular form for a large diameter 50 casing. I

Figure 4 shows in section the manner of rolling a trangular wire from the first pair of rolls into triangular form with arcuate sides for a large diameter casing, the section being taken 55 through the rolls at the left of Figure l.

passing through 1 Figure 5 is a view of the rolls for forming the wire to the shape shown in Figures 3 and 4.

Figure 6 is a view of the finished casing.

On the drawing the numeral 2v indicates a flexible tubing or casing. The tubing is composed of two coiled or intertwined elements 4 and 8. 'The element 4 is relatively flat and has an inside flat surface 8 and an outer arcuate or curved surface ID. The element 6 is in general form triangular, but has its side faces rounded inwardly or in arcuate form as shown at I2. Its top or outer face I4 is also arcuate and rounded inwardly as best shown in Figure 3. The curvature of the side face l2 conforms to the curvature of the side of the elements I as indicated at it. v

Referring-to Figures 1, 4, and 5, the pairs of rollers l5 and l1, l8 and 20 for forming the triangular element 6 are shown. The upper roller I5 is cylindrical while the lower roller l1 has'a V-groove I! to give a preliminary V-shape to the round wire 2!. The second upper roller I! has the annular ribs 22 and 24, while the lower roller has the mating or registering annular grooves '26 and 28. The groove 26 conforms to the rib 22 while the groove 28 conforms to the rib 24. A section through the rib 22 in groove 26 is shown in Figure 4. A circular wire is used and is first passed between the rolls l5 and I! to cause the roller l5 and groove l9 to give it a triangular shape at 6' in Figure 1. This triangular wire is then passed through the rolls l3 and 20 between the rib 22 and groove 26 to give it the flnished shape as shown at 6 in Figures 1 and 3. This shape is used for larger diameter casing.

The form of the rib 24 and groove 28 are dimensionally different but give a finished product of a shape similar to that of Figure 3. The change in shape is to adapt the wire to small diameter casings.

By referring to Figures 3 and 4 it will be noted that the upper inwardly dished curved surface l4 has the outer upwardly projecting edges 30 and 32. When the element 6 is placed in the machine to form the flexible casing 2 to the form shown in Figure 6 the rollers of the machine will flatten or curl down the upwardly projecting edges 30 and 32 and spread them laterally over the surface Ill and cause the element 6 to be substantially flat at its outer surface as shown at 30' and 32' in Figure 2. This flattening or curling down of the edges 30 and 32 which takes place during the forming operation will press the contacting sides at l6 closer together and give to the element 6 and the flexible casing in general a permanent set so that it will not uncurl at the ends and so that there is a much less tendency to break or crack when the casing is given a sharp arcuate curve.

I claim:

1. The method of making flexible tubing consisting of spirally intertwining arelatively flat element having an arcuate surface and a substantially triangular element having arcuate dished sides and an arcuate dished top, the intertwining of said elements into tubular form causing the two arcuate sides of the triangular member to contact with the adjacent arcuate sides oi the relatively flat member and flattening or rolling down of the edges 01' the outer or top arcuate side of the triangular member to cause a flrmer contact between the two spirals and to give a permanent set to the elements of the tubing and to prevent unraveling.

2. The method of making flexible tubing consisting of spirally intertwining a relatively flat element having sloping edge surfaces and a substantially triangular element having sloping sides and a dished top, the intertwining 0! said elements into tubular form causing the two sloping sides of the triangular member to contact with the adjacent sloping sides oi the relatively flat member and flattening or rolling down or the edges of the dished top of the triangular member to cause a firmer contact between the two spirals and to give a permanent set to the elements of the tubing to prevent unraveling.

HARTWEIL W. WEBB. 

